In recent years, navigation system is widely used to guide a traveler to a desired destination. Usually, a global positioning system (GPS) transceiver and a navigation database are employed in the navigation system for obtaining the location of the traveler. Then, the position of the traveler is compared to a desired destination by a central processing unit of the navigation system, and visual and audio indications for guiding the traveling routes to the desired destination can be provided to the traveler via the display and loudspeaker of the navigation system.
In order to facilitate the use of a navigation system in vehicle, a head-up display (HUD) system can be employed for displaying the navigation information to the driver. The head-up display system projects a virtual image onto a specific area of the windshield that is reflected at eye level with the driver. By using the head-up display system, the driver doesn't need to look away from the road to obtain the navigation information. Consequently, the driving safety is enhanced.
US patent application publication No. US 20120191342A1 has disclosed an information displaying system for use with a vehicle head-up display. Referring to FIG. 1, the head-up display system 1 includes a liquid crystal panel 10 and a backlight unit 12 arranged at the rear side of the liquid crystal panel 10. The liquid crystal panel 10 is installed inside of an instrument panel 10a in front of a driver seat so that it can display a driving information image. The backlight unit 12 is used as a light source for irradiating light on the rear surface of the liquid crystal panel 10. The head-up display system 1 further includes an optical unit 14 arranged at the front side of the liquid crystal panel 10 and a reflection mirror 16 installed at the front side of the optical unit 14 at a specific angle. The optical unit 14 is used to enlarge or reduce the driving information image appearing on the liquid crystal panel 10 and to adjust the focal distance of the driving information image projected through the optical unit 14 toward the windshield 18 of the vehicle. Therefore, the driving information image can be displayed on the windshield 18.
However, the optical devices of the conventional head-up display system are installed inside of the instrument panel in front of a driver seat. It is hard for the driver or operator to self install the head-up display system in the vehicle, and the cost of installing the head-up display system in the vehicle is relatively high. In addition, the conventional head-up display system installed in the vehicle can only be used to display driving information image when the vehicle is in use. However, when the vehicle isn't in use, the head-up display system are turned off and can't be taken away from the vehicle to provide various presentation or image display functions outside the vehicle. Furthermore, the conventional head-up display system projecting the light directly upon the specific area of the windshield usually requires a coating material that significantly decreases the transparency of the windshield. As a result, the conventional head-up display system is restricted to limited region upon the windshield.
In addition, the image resolution of the conventional head-up display system doesn't conform to the practical requirements, and the image size projected on the specific area of the windshield can't be well controlled and may be smaller than the specific area of the windshield. Furthermore, the driving information image projected from the conventional head-up display system can only be displayed at the specific area of the windshield, and the conventional head-up display system can't adjust or change the image display height of the driving information image according to the eyes positions of various drivers.
Therefore, there is a need of providing an improved head-up projection system for displaying navigation information to obviate the drawbacks encountered from the prior arts.